During laboratory analysis of body fluid such as blood, a supply of blood serum that is tested for a particular individual is usually contained in a single sample tube. The amount of blood serum in the sample tube is generally of sufficient quantity to allow for repeated aspirations of relatively small amounts of serum, wherein each aspiration is used for a specific test. Thus, a selected amount of sample is aspirated from the sample tube for each test and delivered to one or more processing stations in a sample analysis system.
Each specific, distinctive blood test on an aspirated sample can involve a chemical reaction with one or more reagents. The reactions provide data that forms the basis for sample analysis information that is ultimately furnished to a physician or patient.
An aspiration device such as a syringe or probe is commonly used to aspirate liquid, such as reagent, from a reagent container in predetermined controlled amounts. The aspiration device is also generally used to dispense the aspirated liquid into a reaction cuvette.
In some instances a single aspiration probe may be used to aspirate reagent from more than one container. In one known automated sample analysis system numerous tests are conducted in rapid sequence on blood serum from different individuals. Thus, if one aspiration device is used to aspirate and dispense reagent from more than one container in succession, there will be a residue of reagent from a first reagent container on the aspiration probe when the probe enters a second reagent container. Therefore, the residue of reagent from the first container that remains on the aspiration probe can be carried over to the second reagent container when an aspiration is made from the second reagent container, resulting in a phenomenon known as carryover.
The carryover of reagent from one container to another container adds extraneous material to the other container. Such extraneous or carryover material is undesirable because it can have an adverse effect on test accuracy and lead to erroneous analytical data during sample analysis. The risk of carryover is a deterrent to using the same aspiration probe for successive aspiration-dispense cycles.
One way of dealing with the carryover problem is to change the aspiration probe each time that reagent is aspirated from a container or other liquid holding vessel. The changing of probes every time an aspiration is performed can be an expensive and time-consuming process.
Another way of dealing with the carryover problem is to wash any residue off the probe after each aspiration, before introducing the same probe into another reagent container. The wash process is also time consuming and expensive.
U.S. Pat. No. 6,740,240 to Colville shows an apparatus for sampling and filtering fluid. A piercing device is used to pierce a container cap to enable relatively large quantities of liquid from the container to drain by gravity through the piercing device into a channel. The drained liquid in the channel is then filtered. Colville does not show or suggest how to control the liquid drainage from the container through the piercing device in relatively small precise amounts. Furthermore Colville does not show or suggest repetitive use of the piercing device to obtain numerous expulsions of small precise amounts of liquid from a container.
U.S. Pat. No. 6,471,069 to Lin shows a device for separating components of fluid sample by centrifugation. Lin uses a needle to infuse liquid into a container through a sealable septum. Lin does not show removal of precise amounts of liquid from a container.
It is thus desirable to transfer liquid in predetermined precise amounts from a container or other vessel using a self-contained system that does not include an aspiration and dispense probe.
Corresponding reference numbers indicate corresponding parts throughout the several views of the drawings.